It's not juvenile - as a matter of fact, I'm very wary of Microsoft's moves because I remember perfectly well just how greedy and shady Microsoft has been (especially during the nineties). In comparison, Google has been a much better citizen in the developers community. It too will succumb to the problems of gigantism and the pressure of "shareholder value" in the long run, but for now you really can't compare the credibility of Google's and Microsoft's open source programs.